The present invention relates in general to differential line receivers and, in particular, differential line receivers using gallium arsenide (GaAs) devices.
Differential line receivers are well known in the prior art and have been typically used for transferring data over predetermined lengths of twisted cable or various other types of electrical lines. The differential line receiver receives two signals which are 180 electrical degrees out of phase with each other. The differential line receiver combines these signals into one signal. The advantage of the differential line receiver is the minimization of electrical noise relative to the original signal. The transmitter of the two signals splits the original signal into a positive and negative part which are 180 electrical degrees apart.
Conventional differential stages of differential amplifiers typically use a common, high-impedance current source to achieve gain. Corresponding designs in gallium arsenide do not work well because of complications associated with MESFET's and the forward bias of the Schottky junctions.
The present invention of a gallium arsenide circuit used in a differential line receiver overcomes the problems state above in the prior art. A feature of the present invention is that the line receiver exhibits a substantial degree of immunity to process and temperature variables. A further advantage of this invention is that the line receiver is structurally simple and has a small silicon area requirement. The structural symmetry minimizes sensitivity to temperature and process variables. A further advantage in the present invention is the use of positive feedback to provide gain for the gallium arsenide differential line receiver circuit.
Although the present invention relates to gallium arsenide devices, the invention can also be used with other semiconductor technologies which support MESFET transistor structures. For example, technologies using InP devices.